In short: divide your metered usage (converted to gallons) by the number of days in the billing period, then by the number of people in your household. A 13 CCF (9,724-gallon) monthly bill for four people comes to about 80 gallons per person per day — just under the commonly cited U.S. average of 82.
This figure is only as accurate as your billing period. Confirm the service dates on your bill before comparing to national averages.
How the estimate is calculated
The calculator converts your billed amount to gallons, divides by the number of days in the billing period for a daily household total, then divides again by the number of people:
gal / person / day = (billed amount × unit factor) ÷ billing days ÷ people
CCF (hundred cubic feet) converts at 748 gallons; 1,000 gallons at 1,000; cubic meters at about 264.172 gallons.
Worked example. A 13 CCF bill (9,724 gallons) over a 30.44-day month, for four people, comes to 9,724 ÷ 30.44 = 319 gallons a day for the household, or 319 ÷ 4 = 79.9 gallons per person a day — about 2,431 gallons a month, 29,153 gallons a year, per person.
Converting common billing units
CCF is the most common unit on U.S. municipal water bills. Use this table to sanity-check the calculator's conversion.
| CCF billed | Gallons |
|---|---|
| 1 | 748 |
| 5 | 3,740 |
| 10 | 7,480 |
| 15 | 11,220 |
| 20 | 14,960 |
Why the billing period matters so much
The single easiest mistake with this kind of calculation is guessing the billing period wrong. If your utility actually bills every two months but you divide by 30 days instead of about 61, your calculated daily usage comes out roughly double the truth. Always check the service period printed on the bill itself, since due dates and billing frequency aren't always the same thing.
Unlike a fixture-based estimate, a bill-based figure already reflects everything that actually went through the meter — leaks, guests, seasonal outdoor watering, all of it. That makes it the most accurate figure you can get, provided the billing period is right.
Worked scenarios
Bimonthly bill. A 22 CCF bill (16,456 gallons) over a 61-day bimonthly period, for three people, comes to 16,456 ÷ 60.87 = 270 gallons a day for the household, or 90.1 gallons per person a day — about 10% above the national average.
Gallons billed directly, custom period. A bill showing 15,000 gallons over a 45-day custom period, for two people, comes to 15,000 ÷ 45 = 333 gallons a day, or 167 gallons per person a day — roughly double the national average, worth investigating for leaks or heavy outdoor watering.
Frequently asked questions
What is a CCF and how do I convert it to gallons?
CCF stands for hundred cubic feet, a common unit on U.S. water bills. One CCF equals 748 gallons, so multiply your CCF reading by 748 to get gallons; this calculator does that conversion automatically.
Is my water bill monthly or bimonthly?
Many utilities bill every two months or quarterly rather than monthly. Check the service period dates on your bill, not just the due date, and set the billing period in this calculator to match; assuming monthly on a bimonthly bill roughly doubles your apparent daily usage.
What's a typical gallons per person per day figure?
About 82 gallons per person per day is a commonly cited U.S. average across indoor and outdoor use. Efficient homes with WaterSense fixtures often run closer to 50, while homes with older fixtures or heavy outdoor watering can exceed 120.
How is this different from the household water usage calculator?
The household water usage calculator builds an estimate from fixtures and habits you enter. This tool converts your actual metered bill into a per-person figure instead, so the two are useful together — one to estimate, one to verify against your real bill.
Does this account for outdoor watering already included in my bill?
Yes. Since the figure comes from your actual meter reading, all metered use, indoor and outdoor, is automatically included, unlike fixture-based estimates that sometimes focus on indoor use alone.
What if I don't have a water bill, such as with well water?
If you have a well meter, read it the same way you would a utility meter and enter the reading here. Without any meter, use the household water usage calculator to build an estimate from your fixtures and habits instead.
Sources & references
- U.S. Environmental Protection Agency (EPA). WaterSense: Statistics and Facts.
- U.S. Geological Survey (USGS). Water Q&A: Water use at home.
- Water Research Foundation. Residential End Uses of Water Study (REUWS), Version 2 (2016).
Sarah Bennett, MS
Water Quality & Sustainability Specialist · Portland, Oregon
Environmental scientist (MS, Water Resources) with 9+ years in residential water quality, treatment, and usage efficiency, and 150+ completed assessments. Sarah writes and reviews the treatment, usage, and cost calculators on watercalculator.us. Read full bio
MS Environmental Science, Water Resources (2018) · BS Environmental Engineering (2016)